Furnace conveyer shaft



y ec. E0, E935 o. K. CARPENTER 2,024,024

FURNAC E CONVEYER SHAFT Filed March 5, 1954 2 Sheets-Sheet 1HlllllllL-lgllllllh w, 3935 o. K. CARPENTER FURNACE CONVEYER SHAFT FiledMann 5, 1954 2 Sheets-Sheet 2 .lll

llutll.

attorneys Patented ec. il@ i935 naar as assigner to The lluraldyCompany,

Pittsburgh,

Fa., a corporation of Delaware Application March 5, 1934, Serial No.714,092

5 Claims.

'I'his invention relates to conveyer mechanism and more particularly tohollow roller conveyers such as are employed in high temperaturefurnaces for annealing or heat treating metal or the like.

Heretofore, heat treating furnaces have been constructed in the form oflong kiln-like structures provided with a plurality of roller shaftsextending transversely of the furnace to carry the metal being treatedfrom one end to the other of the furnace. The temperatures employed inthese furnaces, particularly for normalizing low carbon steel, range upto 2000 F.- and sometimes more. As a result of subjecting the rollers tosuch severe operating conditions the rollers often sag, or Warp. Thediscs often become loose on the shafts due to oxidation or wear of theset screws, wedges and the like used to secure the discs in place on theshafts. Discs or wheels formed integrally with the shaft do not have thedisadvantage of loosening on the shaft but increase the cost of n s .fand assembling the shafts in the furnaces.

By the present invention the foregoing and other difiiculties anddisadvantages of prior known roller conveyers have been overcome. Theimproved conveying means of the present invention provides a shaftstrongly resistant to warpage and highly heat resistant with discs orwheels which are independently and positively secured on the dry shaft.The shaft part exposed to high temperatures may be oentrifugally cast soas to eliminate all ordinary casting defects such as shrinkage cavities,lesions, gas pockets, sand inclusions and internal strains. Moreover,the walls of the centrifugally cast shaft can be made of uniformthickness between the strengthening parts and of remarkable density sothat unequal expansion and other strains in the shaft are avoided. Theshaft preferably is made with separate end pieces or trunnions which arewelded to the middle portion ofthe shaft and which extend through thefurnace walls to journal and support the shaft in externally disposedbearing means. The end pieces or trunnions may be cast from somewhatless expensive material which is satisfactory for bearings and supportswithout being particularly resistant to heat.

Likewise by the present invention the wheel discs are mounted on theshaft in a new and novel manner by a positive keying construction withadditional locking means so that the wheels are positively positioned toprevent relative circumferential or longitudinal movement upon theshaft.

The foregoing and other advantages 'of the present invention areachieved by embodiments of the invention described hereafter andillustrated in the accompanying drawings wherein:

Figure l is a plan view partly in horizontal sec- 5 tion of oneembodiment of the present invention.

Figure 2 is an enlarged view of a portion of Figure 1 which betterillustrates the construction of the dry shaft of the conveyingmechanism.

Figure 3 is an enlarged View of a portion of the 10 shaft illustrated inFigure 2.

Figure 4 is a cross sectional view taken Online d-l of Figure 2 andillustrates the manner in which the metal carrying wheels are secured totheA shaft. l5

Figure 5 is a cross sectional view taken on line 5-5 of Figure 4 andillustrates the keying of the wheels on the shaft.

Figure 6 is a view somewhat similar to Figure 2, although morediagrammatic, of another embodiment of the invention.

Figure 7 is an enlarged view of a portion of Figure 6 illustrating howthe trunnions are secured to the main portion of the shaft.

Figure 8 is a cross sectional view taken on line 8 8 of Figure 6 andillustrates another manner of securing the metal wheels on the shaft.

Figure 9 is a cross sectional view taken online 9-9 of Figure 8 andillustrates how the wheels are fastened securely but removably on theshaft.

Referring to the drawings and particularly to Figures 1 and 2 thereof,the numeral lll indicates generally a heat treating furnace havingvertical side walls I2 provided with .a series of openings n Hl throughwhich extend conveyor means or shafts of the present invention, thesebeing indicated generally at it. Each shaft lt comprises a main centralportion i8 which is formed of high heat resisting material and which ispreferably cast by a centrifugal casting operation to form a cylindricalmember of very fine grained, dense, uniform character. The centrifugalcasting operation insures the absense of uneven wall thickness,shrinkage cavities, gas pockets, sand or slag inclusions and internalstrains. The central portion of the shaft IB is preferably formed withone or more integral, longitudinally extending splines 2li as best seenin Figures 2 and 4. These splines 2B are adapted to co-operate withlateral key ways 22 formed in the hubs 2t of wheels 26 which are adaptedto be mounted on the shaft I6.

The wheels 26 are preferably removably secured on the main portion I8 ofthe shaft so that they cannot have relative longitudinal movementthereon and to this end the splines 20 are provided with spaced recesses28 while the hubs 24 of the wheels 26 are provided with apertures 38 sothat locking pins 32 may be utilized to secure the wheels'axially of theshaft. Removable bars 34 serve to lock the pins 32 in position. The bars34 can be welded as at 36 to the wheel 26 to prevent removal.

Welded to the ends of the main portion I8 of the drive shaft I6 aretrunnions il!) which are preferably formed of heat resisting metal inthis embodiment of the invention in View of the fact that they extendsomewhat into the furnace area. The trunnions protrude through thefurnace walls l2 and which are journalled at their ends by suitablebearings 42 and 44. Refractory bushings 46 are ordinarily providedbetween the trunnions 40 and the apertures i4 of the furnace walls l2and these bushings serve to substantially ll the apertures while stillallowing movement of the trunnions therein. Further sealing of thetrunnions inthe furnace wall to prevent a dissipation from heatfrorn'the furnace may be accomplished by providing sealing means 48around the trunnions at the outer sides of the furnace wall.

Referring particularly to Figures 2 and 3 it will be seen that thetrunnions 40 are secured to the main portion I 8 of the shaft by forminga' reduced end 50 on the trunnion 40 with the reduced end being adaptedto extend inside the end of the main portion I8 of the shaft. Thediameter of the main portion I8 and the mating end portion of thetrunnion 40 is substantially the same so that when the portions arewelded together as at 52 a shaft with a smooth outer surface will beprovided.

The trunnions are preferably tapered where they pass through the furnacewalls in order to reduce the size of the trunnions so that thejournalled means can be made smaller and therefore less expensive.Either bearing 42 or 44, but not both, is adapted to prevent lateral oraxial play of the shaft carried thereby; however, the other end of theshaft is allowed to have free axial movement in its bearing so that theshaft is free to expand and contract axially during temperature changes.The shafts may be driven in any suitable manner as for example bysecuring sprockets 56 to the ends of the shafts and providing a chaindrive (not shown) for the sprockets.

In order to reduce as far as possible the expense of conveyer equipmentfor metal treat- .ing furnaces, the present 'invention contemplatesemploying shaft parts composed of heat resisting metals only in thepositions in which they are subjected to high temperatures. Otherportions of the shaft are composed of less expensive metal whereby thetotal cost of the conveying equipment is reduced without sacriiicingitsefficiency and long life. 'I'hus in the embodiment of the inventionillustrated in Figures 6, 7, 8, and 9 the numeral 60 indicates generallya shaft which has a main or central cylindrical portion 62 which iscentrifugally cast to insure uniform wall thickness and absence ofimperfections. The portion62 is adapted to extend at least part waythrough the side walls of the furnace indicated diagrammatically at 64.The cylindrical portion 62 of the dry shaft is of metal ywhich isresistant to heat and oxidation and is, therefore, relatively expensive.Secured to the ends of the cylindrical or main portion 62 of the dryshaft 6U are trunnions 66 -which may be of ordinary metal notparticularly adapted to resist heat inasmuch as the trunnions are awayfrom the furnace area so that they are not subjected to the high heat ofthe interior of the furnace. This construction is less expensive thanconstructions in which high heat resisting material is employedthroughout. Referring to Figure 7, it will be seen that the cylindricalportion 63 of the dry shaft 66 is adapted to receive the telescopingends 68 of the trunnions 66 with the pieces being welded together as at'lll so that together they form a smooth continuous outer surface. Thetrunnions 66 are preferably reduced in diameter at their ends so thatthey can be more readily journalled and driven by means similar to thoseillustrated in Figure 1 and discussed above.

Wheels 12 are preferably secured on the cylindrical portion 62 of thedry shaft 68 and this is accomplished by providing longitudinallyextending splines i4 at a plurality of points on the cylindrical portion62 of the dry shaft. C0- operating with the splines 'i4 are recesses 'i6formed in the wheels 12 and suitable locking keys 18 may be utilized toaxially position the wheels 12 on the shaft. This may be accomplished byproviding recesses 86 at spaced points in the splines 16 which recessesare adapted to receive cylindrical bosses 82 formed on the keys 18. 'Ihekeys 18 may be fastened in place in any known manner such as by weldingindicated at 84.

In both types of shafts illustrated herein and described, it is possibleif desired to circulate some cooling fluid through the interior of theshafts if this is found necessary or desirable.

The assembly or replacement of the dry shafts in the furnace can bereadily accomplished by removing the tops of the journalling pillows,loosening the keying pins, and thereby loosening the wheels I2 or 26 onthe shafts which will then allow the shafts to be slipped out of thefurnace upon removal of the refractory bushing 46 and other sealingmeans 48 at one side of the furnace. New wheel discs can be readilyplaced on the shaft or the shaft can be repaired in any manner eitherwith or without complete removal from the furnace. Reassembly embodiesmerely a reversal of the foregoing procedure.

From the foregoing it will be evident that a simplified practical dryshaft has been provided for use in high temperature furnaces in whichassembly replacement is readily accomplished with a minimum of eort andexpense. The

shaftis adapted to stand up in use over long periods without warping orother undesirable resuits.- The wheels or carrying discs are very firmlyanchored both axially and circumferentially on the shafts which is quitedesirable. The centrifugally cast main portion of the shafts eliminatessubstantially all air or slag inclusions and insures a very uniform wallthickness. The uniform Wall thickness of the cylinder results in a, veryeven expansion and contraction of the shaft with an absence of warpingor stress formation. The elimination of slag and other impuritiesresults in a stronger and longer-lived shaft in which cracking andfailures of all characters are materially reduced. 'I'he longitudinalribs afford resistance to warping while serving as means to preventrelative rotation between the shaft and discs.

It will be appreciated that several embodiments only of the inventionhave been illustrated and described in detail and that the principles ofnoechefe the invention can be utilized in the production oi shafts ofvarious forms. Accordingly the inven tion is not to be limited orrestricted to the types of conveyer mechanism shown and described but isdened by the appended claims.

I claim:

l. A shaft assembly for a high temperature furnace comprising acentriiugally cast cylindri cal tube composed oi high heat -resistingmetal having imperorate walls and having a longitudinally extending,integral, outwardly projecting rib, tapered trunnions of heat resistingmaterial having reduced ends extending into the ends of the tube andhaving shoulders opposed to the end Walls of the tube and weldedthereto, discs on the shaft engaging opposite sides of said rib andmeans securing said discs in place against axial movement relative tothe shaft.

2. A conveyer assembly for a high temperature furnace comprising acylindrical tube of high heat resisting metal, trunnions extending intothe ends of the tube and secured thereto, material carrying wheels onthe shaft in axially spaced position, means removably securing thewheels in position comprising integrally cast longitudinal splines onthe tube which are received in recesses formed in the hubs of thewheels, radially extending pins received in suitable recesses in thesplines within the planes defined by the wheel hubs and means forholding the pins in place.

3. A conveyer assembly for a. high temperature furnace comprising acentrifugally cast cylindrical tube of high heat resisting metal,trunnions into and secured to the ends of the tube, material spi riwheels on the shaft in axially spaced relation, means removably scouring the wheels in position comprising integrally cast longitudinalsplines on the tube which are received in recesses formed in the hubs ofthe wheels, and radially extending pins received in suitable recesses inthe splines and Wheel hubs for preventing axial movement of the wheels.

e. A conveyer assembly for a high temperature furnace comprising acylindrical tube having opposite, integral, longitudinally extendingsplines, trunnions at the ends of the tube, material carrying wheels onthe tube and having recesses formed in the hubs to receive the splines,radial pins in the spline and pin retaining means welded to the wheels.

5. A shaft assembly for a high temperature furnace, including acentrifugally cast cylindrical tube of high heat resisting metal, havingimper-A iorate walls and having an integral rib extending lengthwise onthe outer surface thereof for a major portion of the length of saidtube, trunnions projecting at their inner ends into the ends of saidtube and having shoulders opposed and welded to the end surfaces of saidtube, said trunnions tapering to smaller diameter at their outer ends,disks on said tube engaging opposite sides of said rib and preventedthereby from rotation relative to the tube, and means securing saiddisks against axial movement on said tube.

